Antisurge control and exhaust valve for hydraulic apparatus



Inventor .y

2 SHEETS--SHEET l J. M. TOWLER ET AL ANTISURGE CONTROL AND EXHAUST VALVE FOR HYDRAULIC APPARATUS Filed May 24, 194e A March .25, 1952 March 25, 1952 J., M. TowLER ET A1. 2,590,137

ANTISURGE CONTROL AND EXHAUST VALVE FOR HYDRAULIC APPARATUS Filed May-24, 1946 2 SHEETS--SHEET 2 NOILOHS OIL SUPPLY TANK RELIEF VALVE coNTRoL VALVE PUSH BACK CYLINDERS PRESS CYLINDER i I /nven to f 6 Patented Mar. 25, 1952 UNITED STATES iTENT OFFICE ANTISURGE CONTROL AND EXHAUST VALVE FOR HYDRAULIC APPARATUS Application May 24, 1946, Serial No. 672,067 ln Great Britain May 25, 1945 7 Claims.

This invention relates to piston type control valves used for controlling the admission and exhaust of pressure liquid to and from a press or other hydraulic cylinder, of the kind having means which prevent the valve from being operated fully to open the hydraulic cylinder to exhaust until the pressure in the cylinder has fallen to a safe level, thereby to prevent pressure surge in the hydraulic exhaust main yvvhich would otherwise result if the pressure in the hydraulic cylinder is suddenly released.

In our prior British Patent No. 524,564, we have described a control valve of the above type in which an initial movement of the valve piston or plunger gives restricted or throttled release to exhaust and. further movement to give full exhaust is resisted by a stop consisting'or a small hydraulic ram which is subject to the pressure in the press cylinder under control so that movement of the valve piston to the full exhaust position is prevented until the 'pressure in the press cylinder has fallen to a safe level when the operator can overcome the resistance of the opposing ram and move the valve piston over to the position giving ull exhaust. The object of the present invention is to provide a new method of creating the resistance to free movement of the valve piston which shall be a function of the rate of escape of the liquid to exhaust.

This object is attained in the present invention by designing the exhaust outlet for the initial escape of liquid so as to impose a restriction on said escape suicient to produce back pressure and utilizing said back-pressure to resist free movement of the valve plunger until the backpressure has fallen to the point Where the backpressure can be overcome.

In a control valve according to one embodiment of the present invention the valve plunger has a longitudinal passage drilled up its centre from one end and terminating short of the opposite end so that this latter end is closed. The plunger is formed with a reduced portion intermediate its end to provide a continuous transfer passage around the circumference of the plunger for passing pressure liquid from an inlet to an annular groove in the bore of the valve body from whence it has access to the press cylinder. A further reduced portion forming a groove is provided around the valve plunger and said further groove communicates with the interior of the valve plunger near its closed end by means of radial holes. This groove by suitable longitudinal movement of the valve plunger is brought into registration with the aforementioned annular groove `l iai-46.5)

in the valve bore to open the cylinder oi the press to exhaust.

The opposite or open end of the valve plunger is reduced in external diameter to provide a passage for the exhausting liquid which passes into this passage from the interior of the valve plunger by Way of a further series of radial holes. These holes are of a size initially to impose a restriction on the free escape of liquid to exhaust to ensure that the rate of flow therethrough is less than the rate at which liquid enters the interior of the valve plunger through the rst mentioned radial holes during the initial stage of exhaust thereby to cause a back-pressure to be built up within the hollow valve plunger, suficient to prevent the valve plunger from being moved rapidly to the full exhaust position until the pressure Within the press cylinder has fallen to a level at which it may, with safety, be fully exhausted.

In one example the means for utilizing this back-pressure for the purpose stated comprises a member adapted to eect closure of the open end of the valve plunger and fitted to permit the plunger to move relatively and axially thereto. Preferably this member is in the form of a thimble which is rit ed over the open or reduced end of the valve plunger so as to be a sliding fit thereon, a small spring being fitted inside the thimble to abut against the inner closed end of the thimble and the open annular end` of the valve plunger. This thimble in turn abuts against a stop within the valve casing.

In exhausting the press cylinder with this improvide control valve, the valve plunger is moved by a hand lever towards the thimble and in doing so the small interposed spring becomes partially compressed. This movement is continued until the further reduced portion or transfer groove in the valve plunger overlaps the annular groove in the valve bore communicating with the press cylinder suicient to produce a minute crack through which the liquid to be exhausted can escape at high velocity into the interior of the valve plunger.

The volume of liquid which momentarily is thus permitted to enter into the plunger is greaterY than the volume which can escape freely through the restricted outlet at the opposite end of the valve plunger owing to the very high pressureoi the liquid at the moment of its first entry into the plunger and in consequence a back-pressure is instantly built up within the valve plunger which causes a reaction between the opposing surfaces, constituted on the one hand by the inside face of the thimble and on the other by the inner closed end of the longitudinal passage within the valve plunger, tending to produce axial movement of the valve plunger relative to the thimble which is held stationary by the aforesaid stop. Too rapid opening of the valve causes an excessive quantity of liquid to pass through the minute crack creating an excessive velocity through the restricted passage which in turn creates excessive pressure in the interior of the valve plunger and causes the aforesaid reaction between the opposing surfaces in which said pressure acts. This reaction thus tends to move the valve plunger in the direction to close, or reduce .the area of, the minute crack and so to reduce the rate of pressure fall in the press cylinder to a reasonable amount by reducing the volume of liquid which is permitted to pass through the minute crack. Further opening movement of the valve plunger is thus re sisted until the back-pressure within the valve plunger falls to the point where it may be overcome by the operator when the valve plunger may be moved rapidly to the position of full exhaust. In doing so it may be caused to open a mushroom type valve to let the remaining liquid in the press cylinder escape suddenly to exhaust as by this time the pressure within the press cylinder would have fallen to a safe level.

With the construction outlined above it is possible to open the valve to an undue extent by too rapid and forceful pressure on the operating lever and to avoid this we propose, in a further embodiment, to provide a non-return valve on the end of the valve plunger within the thimble to pass pressure freely to the space at the inner end of the thimble and to prevent the escape of such liquid excepting by way of a restricted space around or across the edge of a piston forming part of the non-return valve structure. By this refinement sudden movement of the valve plunger is prevented by the dash-pot action of the liquid trapped within the thimble. Similarly, even when the back-pressure which holds the plunger against movement has fallen to the point where it may be overcome by the operator, subsequent movement of the plunger is constrained, by the same dash-pot action to be gradual and even.

In order that the invention may be clearly understood and carried into effect the embodiment which comprises a dash-pot will now be described, by way of example, by aid of the accompanying drawings in which:

Fig. l is a longitudinal section through the complete valve.

Fig. 2 is a detail showing the thimble and dashpot device to an enlarged scale.

Fig. 3 is a diagrammatic view showing the association of the elements in the operative assembly.

In the example illustrated the control valve has a valve member in the form of a packing-less piston I or plunger which is mounted to slide longitudinally in a bore 2 relatively to three annular grooves, 3, 4 and 5 in the valve body. The groove 3, communicates with the press cylinder, the central groove 4 with the pressure supply main or pump and the groove 5 with the pushback cylinder s) of the press. Pressure liquid from the groove 6 is admitted to grooves 3 and 5 alternately by a continuous transfer passage S formed by a section o reduced diameter in the length ci the valve plunger, and as a result of suitable longitudinal movement of the valve plunger. This movement is imparted by a hand lever l and longitudinal movement of the plunger to the right from the neutral position shown is resisted by a spring 8 or other load which tends to urge the plunger back to its neutral position again when the pressure imposed by the hand lever is removed.

All of the above is of course common practice but in the improvement of the present invention a longitudinal passage il is bored up the centre of the valve plunger from the left hand end, to a point just beyond the groove 3 when the plunger is in the neutral position which opens its left hand end whilst leaving its right hand closed. This longitudinal passage is adapted to be opened to the groove 3 on suitable movement of the valve plunger to the left for which purpose the plunger at this end is formed exteriorly with a circumferential groove I0 and a series of radial holes II connecting said groove with the passage 9 near its closed end.

The left hand end of the Valve plunger is reduced externally in diameter to form two stepped sections, an inner and larger stepped section I2 to provide with the surrounding valve body an annular passage I3 for the exhausting liquid and an outer and smaller stepped section I4 to form a mounting for the slidable reception of a thimble I5. The passage 9 within the valve plunger communicates with the annular passage I3 by means of radial holes I6. These holes have a diameter which is a predetermined so that their total area imposes a restriction on the free escape of liquid from the passage 9 during the initial exhausting of the press cylinder suicient to cause a back-pressure to be built up within said passage sufficient to prevent the valve plunger from being moved over rapidly to the position of full exhaust as hereinafter described. The resistance thus imposed by the back-pressure upon movement of the valve plunger to the left results from a reaction between opposing but relatively and axially movable surfaces consisting on the one hand of the closed end of the passage 9 and on the other hand by the closed outer end of the thimble in view of the following.

As previously explained the thimble i5 is free to slide upon the reduced section I4 of the valve plunger and is restricted from rotational movement by a cotter pin Il the ends of which engage in opposing longitudinal slots IS in the wall of the thimble. These slots are closed at both ends so that the valve plunger, in its movement to the right, is prevented from withdrawing itself from within the thimble.

In operation the valve plunger with the thimble are movable freely to the left until the outer closed end of .the thimble contacts with an opposing abutment I9 when continued movement of the valve plunger to the left must be relative to the thimble. This continued movement is permitted until exhaust commences when further relative movement is resisted by the reaction of the aforesaid back-pressure and in the hands of a careful operator this resistance would be suiicient to restrain him from using the excessive force neces sary to overcome it. It is advisable however to render impossible movement of the valve plunger to cause undue opening of the press cylinder to exhaust by a too rapid and forceful pressure on the operating lever. To this end we ensure that liquid is trapped within the thimble in such manner as to produce a dash-pot action. For this purpose a non-return valve is provided on the left hand end of the valve plunger which will pass liquid freely to the interior of the thimble but which will prevent its escape except at a cornparatively slow rate. This non-return valve comprises a rubber pad 2|) vinterposed between a pad piece 2| affixed within the open end of the passage 9 inthe valve plunger by the cotter pin and a loose Valve member 22 having a valve face which is pressed against the rubber pad by a spring 23. The exhausting liquid passes the valve member 22 and enters into the space 24 at the back of said valve member 22 by way of passagesA 25 vthe passages associated with the pad piece 2| being disposed on either side of the cotter pin and the passage of the valve member passing through the centre of the same, but the escape the same way of the liquid within the space 24 is prevented by the action of the rubber pad. Such escape must therefore take place through a restricted space, which, in the present example, is represented by the clearance between the peripheries of the valve member 22 and the pad piece 2| and the surrounding wall of the thimble. It will thus be s een that the liquid so trapped will prevent the valve plunger with the non-return valve elements from boing pushed into the thimble and that even when the back-pressure has fallen to the point where it may be overcome by the operator such relative movement of the valve plunger must perforce be gradualand even and its rate determined by the rate at which the trapped liquid can escape.

The liquid in the press cylinder in escaping to exhaust must pass through the exhaust outlet 26. This it does initially and, at the required restricted rate by way of the longitudinal passage 9, restricted outlets IE, and annular passage I3. Full and free exhaust however, takes place past a mushroom valve 21 from a space 28 on its outer side which space is in constant communication with the annular groove 3 by way of passages 29. The mushroom valve 21 is thus held rmly on its seat by the pressure of the liquid in the space 2a and is forced open by pressure from its other side when the pressure in the press cylinder has fallen to a suiiiciently low figure. This pressure is applied by the outer end of the thimble when in contact with the abutment I9, which is carried by the end of the spindle 30 of the exhaust valve 27, as a result of movement of the valve plunger to the left by operation of the hand lever To open the press cylinder to exhaust with a control valve as above described the valve plunger is moved to the left to bring the thimble into contact with the abutment I9 and partially to compress the spring 23. As a result of this partial or initial movement a minute crack is provided through which pressure liquid may escape at high velocity into the longitudinal passage 9. Further movement of the valve plunger is now resisted both by the reaction due to the aforesaid back-pressure and by the liquid locked within the thimble. The press cylinder thus continues to exhaust at a restrained rateuntil the pressure within the press cylinder has fallen to a safe level when the operator is enabled to overcome the back-pressure and move the valve plunger still further to the left until the; end of the plunger meets the opposing end of the thimble when continued movement to the left serves to force the mushroom valve 2l off its seat and permit the press cylinder to exhaust freely and directly through the exhaust` outlet 28. When exhaust is complete the valve plunger will be returned again to its neutral position by the spring 8. This spring is so arranged that trai position to the. left and the mushroom valve is returned to its seat by its spring 3|.

We claim:

1. In a hydraulic apparatus of the kind speci fied wherein a reciprocating plunger valve controls the admission and exhaust of pressure liquid to and from a hydraulic cylinder; an exhaust outlet from the hydraulic cylinder, a plunger valve having a valve plunger presenting a transverse pressure area, a resistance element presenting a transverse pressure area in opposed relation to said first mentioned area, an inlet for exhaust liquid from the hydraulic cylinder formed at one end of the plunger valve and a restricted outlet for exhaust liquid formed at the other end of said plunger valve, said inlet and outlet being connected by the interior of said plunger valve, the exhaust inlet of said valve plunger being initially opened to the exhaust outlet of the hydraulic cylinder in a minute amount upon displacement of the plunger valve, the exhaust outlet of the plunger valve being formed as to impose a restriction on the free escape of exhaust liquid flowing through the plunger valve, said areas being exposed to the pressure of exhaust liquid flowing through said plunger. valve, whereby the exhaust liquid entering into and passing through the said valve plunger builds up a back-pressure at the exhaust outlet thereof reacting on said areas and suflicient to resist further longitudinal movement of the plunger valve towards increasing the amount of opening of the exhaust inlet thereof until the velocity of the exhaust liquid ilow through the valve plunger and the consequent backpressure produced at the exhaust outlet thereof has fallen.

2. In a hydraulic apparatus of the kind specied wherein a reciprocating valve plunger controls the admission and exhaust of pressure liquid to and'from a hydraulic cylinder, an exhaust outlet from the hydraulic cylinder, a hollow plunger valve having a valve plunger presenting a transverse pressure area, a resistance element presenting a transverse pressure area in opposed relation to said first mentioned area, an inlet for exhaust liquid from the hydraulic cylinder formed at one end of the plunger valve and a restricted outlet for exhaust liquid formed at the other end of said plunger valve, said inlet and outlet being connected by the hollow interior of said plunger' valve, the exhaust inlet of said valve plunger being initially opened to the exhaust outlet of the hydraulic cylinder in a minute amount `upon displacement of the plunger valve, the exhaust outlet of the plunger valve being formed as to impose a restriction on the free escape of exhaust liquid iiowing through the plunger valve, said areas being exposed to the pressure of exhaust liquid flowing through said plunger valve, whereby the exhaust liquid entering into and passing through the hollow of said valve plunger builds up a backpressure at the exhaust outlet thereof reacting g on said areas and suflicient to resist further by movement of the valve plunger from the neulongitudinal movement of the plunger valve to,-`

wards increasingy the amount of opening of the exhaust inlet thereof until the velocity of the exhaust liquid now through the hollow of the trols the admission and exhaust of pressure liquid to and from a hydraulic cylinder, an exhaust outlet from the hydraulic apparatus, an exhaust outlet from the hydraulic cylinder, a plunger valve having a valve plunger presenting a transverse pressure area, a resistance element presenting a transverse pressure area in opposed relation to said rst mentioned area, an inlet for exhaust liquid from the hydraulic cylinder formed at one end of the plunger valve and a restricted outlet for exhaust liquid formed at the other end of said plunger valve, said inlet and outlet being connected by the interior of said plunger valve, said inlet being also connected to the exhaust outlet of the hydraulic apparatus, the exhaust inlet oi said valve plunger being initially opened to the exhaust outlet of the hydraulic cylinder in a minute amount upon displacement of the plunger valve, the exhaust outlet of the plunger valve being formed as to impose a restriction on the free escape of exhaust liquid flowing through the plunger valve, said areas being exposed to the pressure of exhaust liquid ilowing through said plunger valve, whereby the exhaust liquid entering into and passing through the said valve plunger builds up a back-pressure at the exhaust outlet thereof reacting on said areas and sufficient to resist further longitudinal movement of the plunger valve towards increasing the amount of cpening of the exhaust inlet thereof until the velocity of the exhaust liquid flow through the valve plunger and the consequent back-pressure produced at the exhaust outlet thereof has fallen.

4. A piston or plunger type anti-surge control and exhaust valve of the kind specied for hydraulic apparatus of the kind specied having means which utilize back-pressure created by the exhaust liquid to resist free movement of the valve piston or plunger until the pressure within the cylinder of the hydraulic apparatus has fallen to the point where the back-pressure can be overcome, said means comprising a longitudinal passage within the interior of the valve plunger and a transverse pressure area exposed to the pressure in said passage, said passage being closed at one end, a thimble mounted for relative sliding movement on the valve plunger for closing the opposite end of said passage and presenting a pressure area opposed to said iirst mentioned area, a stop adapted to be contacted by the outer end of said thimble-in the longitudinal movement of the valve plunger to open the hydraulic cylinder to exhaust, an inlet for exhaust liquid adjacent the closed end of said passage, which opens initially to the extent of a minute crack following a small relative movement between the plunger and the thimble and an outlet adjacent the opposite closed end of the passage, said outlet having an area such as to impose a restriction on the free escape of the exhaust liquid from the interior of the valve plunger suicient to cause a backpressure to be built up within the interior of the valve plunger at the commencement of the exhaust to resist through reaction on said areas continued longitudinal movement of the valve plunger towards and relative to the closure member or thimble when said member or thimble is in abutting engagement with said stop until the velocity of the liquid escaping from the interior of the valve plunger has fallen to the point where the back-pressure can be overcome by the operator.

5. An anti-surge control and exhaust valve according to claim 4 wherein the passage in the valve plunger is separated from the interior of the thimble by a non-return valve which operates to pass exhaust liquid freely from the passage to the interior of the thimble but prevents its escape in the opposite direction, excepting by way of a restricted space, through leakage around a piston forming part of the non-return valve structure whereby sudden movement of the valve plunger relative to the thimble is prevented by the dash-pot action of the entrapped liquid.

' 6. An anti-surge control and exhaust valve according to claim 4 wherein full exhaust of the hydraulic cylinder takes place through an outlet which is normally closed by a valve the stem of which carries the stop with` which the thimble is caused to contact said valve being opened by pressure imposed on the stop through the thimble by the movement of the valve plunger which iollows the overcoming of the back-pressure.

7. In a hydraulic apparatus of the kind specied, wherein a plunger valve reciprocating within a bore controls the admission and exhaust of pressure liquid to and from a hydraulic cylinder said plunger valve having a transverse pressure area, a restriction element having a transverse pressure area opposed to said rst mentioned area, an exhaust outlet leading from the hydraulic cylinder, an inlet for exhaust liquid from the hydraulic cylinder at one end of the bore, and a restricted outlet for exhaust liquid received from the hydraulic cylinder at the other end yof said bore, the inlet and outlet aforesaid being connected by a passageway in the bore, said areas being open to said passageway, the exhaust outlet of the bore being formed as to impose a restriction on the free escape of exhaust liquid flowing through the passageway in the bore, the exhaust inlet of said bore being initially opened to the exhaust outlet of the hydraulic cylinder in a minute amount upon displacement of the plunger valve, whereby the exhaust liquid entering into and passing through the said bore builds up a back-pressure at the exhaust outlet thereof through reaction on said areas sufficient to resist further longitudinal movement of the plunger valve towards increasing the amount of opening of the exhaust inlet thereof until the velocity of the exhaust liquid flow through the bore and the consequent back-pressure produced at the exhaust outlet thereof has fallen.

JOHN MAURICE TOWLER. FRANK HATHORN TOWLER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,367,241 Stacy Jan. 16, 1945 FOREIGN PATENTS Number Country Date 5,430 GreatV Britain of 1896 524,564 Great Britain Aug. 9, 1940 

